Carbon Nanotubes And Graphene Supported MnCo₂O₄ As Non Precious Metal Catalysts

With the continuous development and progress of society,the human demand for clean energy is increasing day by day.Hydrogen as a raw material for renewable hydrogen fuel cell came into being.The performance of renewable hydrogen fuel cell depends mainly on the oxygen electrode reduction-reaction?ORR?and oxygen evolution reaction?OER?,At present,the platinum-based precious metal is the best catalyst,but limited by its high cost,short life and other defects of the constraints,this catalyst can not large-scale commercial develop.Therefore,the development of low-cost,high life,good catalytic performance of the new catalyst is imminent.Spinel structure of MnCo₂O₄ is confirmed to have excellent catalytic performance both in oxygen evolution reaction and oxygen reduction reaction.It has good stability,low price,rich in resources,environmental protection and many other advantages.MnCo₂O₄ is a very promising development potential of renewable hydrogen fuel cell cathode catalyst.However,as an oxide,MnCo₂O₄ is restricted by its low electrical conductivity,which is unfavorable for fast electron transfer.Therefore,in this paper MnCo₂O₄ is combined with carbon nanotubes?CNTs?and graphene?G?to take full advantage of their catalytic activities.Composite catalysts containing MnCo₂O₄ and CNTs are synthesized using hydrothermal method combined with vacuum heat treatment.When the vacuum heat treatment temperature is 500?,the pure spinel structure MnCo₂O₄ is obtained.The MnCo₂O₄ has a rough surface which make it has a large specific surface area.The MnCo₂O₄ particles is wrapped by CNTs and not easy to fall off,contributing to a good cycle stability in alkaline solution.The average electron transfer number between the potential of-0.4 and-0.6 V is 3.83,the oxygen reduction reaction catalytic activity is close to commercial Pt/C.The performance of catalytic oxygen evolution reaction capacity is much higher than the commercial Pt/C.It also shows better catalytic activity for oxygen evolution reaction with a current density of 10 mA cm-2 at 0.76 V?vs.Hg/HgO?.The composite catalyst MnCo₂O₄/G is prepared by microwave-coprecipitation method.The average size of the catalyst particle are about 50 nm,They grow on graphene dispersedly.The average electron transfer number between the potential of-0.4 and-0.7 V is 3.85,The initial potential is 0 V,the half-wave potential is-0.12 V and the limiting current density is 5.41 mA / cm²,the oxygen reduction reaction catalytic activity is close to 20% Pt/C,but the cycle stability is higher than Pt/C.It also shows better catalytic activity for oxygen evolution reaction.When the current density is 10 mA / cm²,the catalytic oxygen evolution reaction potential is 0.78 V?vs.Hg/HgO?.Indicating that the catalyst has high catalytic activity both in oxygen reduction reaction and oxygen evolution reaction.